This invention relates to railway systems and more particularly relates to a novel and improved rail adaptable for use in electric transit systems of metropolitan areas.
It has been proposed in the past to utilize resilient pads beneath the lower flanges of railroad rails as well as railroad ties for cushioning the rails and insulating them electrically from the ties and from other underlying structures. In many cases, clamps are employed on opposite sides of the lower flange which are in turn anchored into the railroad ties or rail bed. Also, in some cases an adhesive is interposed between the pad and the rail.
Different considerations are involved in the construction and installation of rails for urban transit systems which are typically employed as a part of electrical transit systems and must be mounted in asphalt or concrete roadways. Instead of a gravel or dirt roadbed the rails are embedded in spaced parallel channels formed out of the existing roadway such that the top or head of the rail projects slightly above the upper end of the channel or roadway surface. In the past, rubber boots have been loosely disposed in surrounding relation to the bottom flange of the rail and typically held in place with the use of clamps extending along the entire length of the rail system. This approach has been unsatisfactory particularly from the standpoint of complete vibration and sound-proofing as well as providing the necessary resistance to corrosion resulting from stray electrical current. In stray current corrosion, an electrical current flowing in the environment adjacent to a structure causes one area on the structure to act as an anode and another area to act as a cathode. For example, in an electric railway, a pipeline or other structure may become a low resistance path for the current returning from the train to the power source. Whenever the pipeline is caused to be more positive by the stray current, corrosion occurs at a higher rate but can be avoided by proper insulation of the rail.
Over extended periods of time, rail systems of the type described have been wholly inadequate to achieve the necessary vibration and sound-proofing and to avoid corrosion from stray or leakage current of the types described.